The use of glass as reinforcement for cementitious materials such as concrete has been investigated for many years. Consideration has been given to the use of glass fiber rods to replace conventional steel reinforcement, as well as to the use of glass reinforcement in the form of fibers, flakes and woven or non-woven fabrics. Particular attention has been given recently to the use of glass fibers as a reinforcement for concrete and cement.
A serious obstacle in employing glass as a reinforcement in cement and concrete is the alkaline environment of the inorganic cementitious binder, which is highly deleterious to the glass and results in significant loss of strength in the reinforced cement or concrete products over a period of time, or even in total destruction of the glass reinforcement. Attack and destruction of the glass reinforcing properties is particularly rapid under humid conditions.
Prior approaches to overcoming the problem of alkali attack of the glass reinforcement have included the use of low alkali type cements, the use of coatings to protect the glass from the alkali, the use of specialized alkali resistant glass compositions, and the use of a cation exchange material to change the inorganic alkaline binder into a form which does not attack the glass. The most active areas of investigation appear to be the use of protective coatings for the glass and the development of alkali resistant glass compositions, as evidenced, for example by several very recent patents, e.g., U.S. Pat. Nos. 4,002,482, issued Jan. 11, 1977 and 4,013,478, issued Mar. 22, 1977.
However, the above-mentioned prior approaches have not been entirely successful in producing a practical, commercial glass reinforced cement composition. The limited availability and expense of the specialized materials required in these approaches renders the use of these materials unfeasible for many applications.